In the field of bio-preservation, one of the most successful and well-known processes is the process of freeze-drying. Freeze-drying is the process of freezing a product under a high vacuum to extract most of the moisture from the product and then by heating the same product under vacuum in a vacuum chamber to extract the small amount of moisture that is left in the product.
The process of freeze-drying was originally implemented during World War II as a method for preserving blood plasma and pharmaceuticals. Eventually it became a recognized method for preserving fruits, vegetables, and other commercially grown bio-products. More recently, freeze-dry methods are being used in a variety of technical fields from chemical processing to producing super computer conductors.
The most common freeze-dry operations are those that process fruits, vegetables, herbs, and other consumables that are commercially available. The main purpose for employing the freeze-dry method is not an economic one, but rather that it is arguably the most successful preservation method for extracting water from a product wherein the cellular structure of the product is least damaged, allowing for better reconstitution of the product to most closely resemble it's natural state before drying.
There are small, moderate, and very large commercial freeze-drying systems available and in commercial operation Typically, companies that provide commercial freeze-drying services to other entities maintain the largest commercial freeze-dry systems. Some utilize multiple (20 or more) vacuum chambers each having a diameter equal to or greater than 6 feet. These are the systems that usually can be contracted and work as batch units drying multiple product batches simultaneously on a large commercial scale.
The basic components of a freeze-dry system are a vacuum chamber supporting shelves for product placement, a condenser, a condenser refrigeration unit, a vacuum pump for providing a vacuum in the chamber, and a heat-transfer/cooling system integrated, in most cases with the product shelves for temperature controlled heating and cooling. Freeze-dry systems are typically operated from a control panel that provides program control over, temperature, vacuum pressure, time, and so on. Different types of products require different measures of control to produce the best result in freeze-drying. In some simpler cases the condenser, which is in the chamber for collecting water vapor as ice, is not equipped to be heated to melt the ice after a run, but the ice is mechanically removed, such as by chipping or scraping, or melted by spraying the condenser with water.
Production of wastewater, generally referred to in this specification as effluent, is one aspect of the freeze-dry process, the wastewater resulting from the moisture extracted from the products being dried. The way the process works is that the product is frozen before undergoing vacuum. At higher vacuum levels the water in the frozen state is vaporized (sublimated) without entering a liquid stage by maintaining an unbalanced state between the ice and the temperature/vacuum conditions. The water vapor produced from the solid ice eventually forms on the much colder condenser as ice crystals. The condenser may take several forms like a coil system, a cone-shaped apparatus, an array of plates, and so on. The condenser is cooled using a refrigeration unit to a temperature lower than the chamber temperature under vacuum causing the extracted vapor to collect on the condenser in the form ice crystals.
After freeze-dried product is removed and the temperature rises, the ice crystals typically melt and fall to the floor of the vacuum chamber (internal condenser) or condenser housing (if external) during a defrost operation. Manual methods may be used to scrape or chip the ice, as described also above; or water or other material, for example, may be used to melt the ice. The moisture is typically output from the system as wastewater.
It has occurred to the present inventor that the wastewater produced by freeze-dry operations could, if properly reclaimed, be used for many interesting, advantageous, and unique purposes, rather than being discarded into the sewer system or dumped as a waste product.
Therefore, what is clearly needed are methods and apparatus for recovering the effluent extracted from products that have been freeze dried, and methods for use of recovered product.